The need for sedative therapy in mechanically ventilated patients in adult and pediatric critical care settings is well established. The overall goals of sedation in the critical care setting are to provide physiologic stability, ventilator synchrony and patient comfort. The use of inappropriately high or low levels of sedation in critically ill adults and children is accompanied by significant risks. Sedation management is a multidisciplinary process but in 94% of ICUs, nurses are primarily responsible for decision-making about administration and titration of sedation. Nurses adjust sedation based on a wide range of non-systematic information which may result in either inadequate or excessive sedation. Without a clear understanding of whether present use of sedative therapy is successful in achieving all sedation goals, it is not possible to devise methods to optimize the evaluation and management of sedation. Therefore the specific aim of this prospective study is to determine the effect of sedation in achieving sedation goals (physiologic stability, ventilator synchrony and comfort) in mechanically ventilated patients across populations. A secondary aim is to identify subject and sedative factors that affect achievement of sedation goals. A total of 200 subjects (ages 2 years and older) from one pediatric and 3 adult ICUs will be enrolled over a 2 year period. Each subject will be monitored for 24 hours to determine achievement of sedation goals. Sedation level will be measured continuously using the Patient State Index. Physiologic stability will be measured by continuous HR, SpO2, RR and heart rate variability. Ventilator synchrony will be measured by continuous airway pressure and observed synchrony. Comfort will be measured using continuous wrist actigraphy and continuous EMG of facial and forehead grimacing. All data will be collected by research team members and downloaded to a computer for analysis. Descriptive statistics of all variables will be performed. The natural history over the 24-hour period will be described using time plots for each of the measurements, identifying amount of time in a 24 period that sedation goals have been achieved for each subject. Repeated-measures logistic regression models will then be developed for primary as well as secondary outcomes and a single multivariable model will be developed with the primary outcome measures considered simultaneously.